Carburetor



. Jan. 19, 1932. R. F, BRACKE CARBURETOR Filed Nov. 50, 1927 PatentedJan. 19, 1932 UNITED ST TES PATENT 1 OFFICE ROBERT F. BRACKE, O'FCHICAGQ'ILLINOIS, ASSIGNOR TO CURTIS B. CAMP, TRUSTEE,

CARBURETOR OF GLENCOE, ILLINOIS Application filed November 30, 1927.Serial No. 236,613.

' My invention relates to improvements in.

5. an improved carburetor.

A further object is to provide a carburetor which, under all normaloperating, operates with maximum fuel economy, but in which, at or nearwide open throttle position, a relatively greater quantity of fuel maybe delivered to the induction passage.

A further object is to provide a carburetor in which the fuel economizerfunctions in such a wayas not to reduce the efliciency of the fuellifting properties of the carburetor, but which actually increases theseproperties below three-quarters open throttle position.

A further object is to provide a carburetor which precludes the presenceof too rich a mixture in the induction chamber at less thanthree-quarters throttle position.

A further object is to provide a carburetor which eliminates thepresence of gas or air bubbles in sufficient quantity in the fuelchamber to impair the uniform flow of fuel to the primary intake or fuelnozzle, thus preventing the passage of the fuel from the fuel chamber inslugs separated by air pockets.-

A further object is to provide a carburetor in which air bubblescollecting in the fuel chamber are continuously drawn into and comingledwith the fuel stream passing there- ,from so as to prevent theaccumulation of relatively large quantities of air in the fuel chamber.7

Other objects and advantages will be more particularly pointed out inthe following specification and appended claims.

The carburetor is illustrated in' the accompanying drawings forming apart of this application, in which. v

Figure 1 is a sectional view of the carburetor' and a fuel supplv tank;

Figure 2, a view along the line 2-2 of Figured, and

Figure 3 is a fragmentary sectionalview of a modified form of a part ofthe carburetor illustrated in Figure 1.

The invention will be explained as embodied in that type of carburetorwhich I have fully illustrated and explained in my co-pendingapplication for a patent on vacuum feed carburetors, Serial No. 155,598,filed December 18, 1926, and consists chiefly, with reference now to thedrawings, in an.- induction chamber 1, a secondary air inlet 2, and adelivery passage 3 having its mouth adapted for registration andconnection with the intake manifold 4 of an internal com-- bustionengine. The chamber 1 and the passage 3 constitute, and shallhereinafter be referred to as, the induction passage of the carburetor.

The carburetor further consists of a spring pressed air valve 5 whichopens against the tension of a spring 6 by atmospheric pres sure topermit the passage of air from the secondary air inlet tube to theinduction passage of the carburetor. A fuel chamber 7 communicates bymeans of a passage 8 with the throat 9 of a primary-inlet 10 having theform of a Venturi tube. The Venturi tube is projected laterally througha wall of the chamber 1 and extends to a point near the center of thechamber where the thoroughly atomized fuel and air is delivered thereto.The opposite end of the tube is subjected to atmospheric pressure. Aspring pressed and normally closed fuel valve 11 is provided in the fuelchamber? for controlling the passage of fuel from the chamber 7 to thepassage 8. This valve is operated by a diaphragm 12, one side of whichis subjected to atmospheric pressure.

As explained in the co-pending application referred to the passage ofair through the primary air inlet or Venturi tube 10 creates. arelatively high suction in the throat 9 due to the suction multiplyingprinciples of the Venturi tube. This suction is communicated to the fuelchamber below the diaphragm,

causing the diaphragm to move through atmospheric pressure and open thevalve 11,

draw fuel from a supply tank 13 up, into the fuel chamber 7 throughadeliver tube 14.

A principal feature of my invention consists in a valve 15 disposed inthe fuel passage 8 for restricting the flow of fuel to the throat 9 ofthe primary air passage 10 at all points below three-quarters to wideopen throttle position. I refer here to the butterfly throttle 16disposed in the passage of the carburetor and which is operated bymovement of an arm 17 extending radially therefrom exteriorly of thecarburetor. I thus cut down to a practical minimum, without sacrificingefiiciency, the quantity of fuel admitted to the induction passage atall points below three-quarters throttle position.

The valve 15 has a stem 18 extending upwardly (see Figure 2) to a pointadjacent to that end of the throttle shaft 19 remote from the arm 17. Acam 20 is carried on this portion of the shaft and secured thereto byscrew 21 which falls off abruptly at 22 so as to permit a normallycompressed spring 23 disposed beneath the valve to close the valve whenthe shaft is turned in the direction of the arrow 24 to a point belowthree-quarters open throttle position. Theyalve does not entirely closethe passage 8 as I have provided a by-pass 25 through the valve which issufliciently large to accommodate .all of the fuel necessary for theeflicient operation of the carburetor throughout the normal and lowspeed ranges. I

As the suction multiplying property of the Venturi tube depends upon thequantity and velocity of air passing therethrough and not upon anobstruction in the delivery passage to the throat, I do not in anywisereduce the depression in the Venturi tube, below that necessary tooperate the diaphragm against the spring pressed valve, though I doreduce the quantity of fuel that is admitted thereto through theopenings 27 in the throat 9.

In order to clarify the illustration of the various parts of thecarburetor I have shown, in Figure 1, the valve 15 and the throttleshaft as disposed'in the same vertical plane as that of the Venturi tube10. In practice, however, this valve should be in a plane out of that ofthe tube 10 so that there would be no possibility of its presenceobstructing in any way the inlet orifice 80 of the venturi which, forefiicient operation thereof, must be entirely exposed and accessible toatmospheric pressure. I

It has been found that in carburetors of the fuel lift type which employsuction means in suchstructure herein illustrated, beneath the diaphragm12 which constitutes the uppermost part of the chamber. The presence ofair in relatively large quantities causes at certain times the passageof the fuel through the delivery passage 8 in slugs with inter posed airpockets. As a result of this passage of air in relatively largequantities, the carburetor functions so as to cause the engine to missand operate erratically. T o overcome this disadvantage I have providedtwo fuel passages for conducting fuel from the cham' ber 7 to thepassage 8. The larger of the two, 28, communicates with the chamber 7immediately beneath the diaphragm 12. The smaller passage 29communicates with the chamber 7 at a point well beneath the top ofthechamber so that no air bubbles may pass therethrough.

The passage 28 draws fuel and air bubbles as fast as they accumulate atthe top of the fuel chamber into the passage 8, where they are comingledwith a substantially solid fuel column admitted through the smallerpassage 29. The result of the meeting of the streams from the passages28 and 29is such that the bubblesv which enter through the passage 28are quite thoroughly comingled with the composite fuel stream of bothpassages, and any large bubbles are broken up. This entirely precludesthe presence of air in sufficient quantities at any time in the passageto cause erratic action of the engine.

In operation throughout the normal low speed ranges of the vehicle uponwhich the carburetor is used, the throttle 16 will remain belowthree-quarters open throttle position.

The cam 20 during this time is disengaged from the upper end of thevalve stem 18 so as to permit the valve 15 to remain closed by virtue ofthe compression spring 23, as shown in dotted lines in Figure 1.

In this manner the valve 15 permits the passage of fuel only through theby-pass 25 so that the quantity of fuel which may be drawn into theVenturi tube 10 and delivered into the induction passage is less thanthat available when the valve is open. The closed valve with by-passdoes not in any way impair the fuel lifting properties of the Venturitube so that there is no possibility of the suction created therebyfalling below that degree necessary to lift fuel from the tank 13 intothe chamber 7. When, however, the throttle 16 is open beyondthree-quarters open position, the cam 20 moving with the shaft of thethrottle valve engages with the stem 18 of the valve to open the valveto that position shown in full lines in Figures 1 and 2. This operationof the valve permits maximum flow of fuel to the Venturi tube 10 and inturn to the induction passage only when required for high' speed or fullload operation of the vehicle.

Air in the form of bubbles accumulated beneath the diaphragm 12 will beconstantly withdrawn through the passage 28 into the passage 8 as fastas the bubbles are formed and rise to the-top of the fuel chamber. Thiscontinuous exhausting of the fuel chamber of bubbles precludes allpossibility of accumulaa Venturi tube forming a primary air inlet,

tion of sufficient air to cause erratic engine operation. In Figure 3 Ihave illustrated a modified formof the bubble eliminating structure in 5which I employ a threaded plug 32 havingia relatively long narrowpassage 33 there through which communicates at one end with to break uplarge bubbles into small bubbles I 5 as they pass into the passage 8:The fuel admitted through the passage 33 subsequently to the passage ofthe bubbles into the passage 8 is united with the comingled air and fuelto distribute'and again divide the bubbles into smaller ones.

I claim: 1. The combination in a carburetor having a primary air inletin the form of a Venturi tube, a passage for conducting. fuel to thethroat of the Venturi tube, a throttle valve for controlling the egressof fuel mixture from the carburetor, a normally closed valve having aby-pass interposed in the fuel pasconnecting at its opposite end throughtwo passages with the fuel chamber, one of -the passages being wellbeneath the level of fuel in the fuel chamber and the other at theuppermost part of the fuel chamber, said latter passage serving toconduct air bubbles from the fuel chamber into the fuel passage to thenozzle.

3. The combination in a carburetor having a primary air inlet in theform of a Venturi tube, a fuel chamber, a passage interconnecting thefuel chamber and the throat of the Venturi tube for drawing fuel fromthe chamber into the Venturi tube by the suction created upon thepassage of air through the tube, a throttle valve controllingthe egressof fuel mixture from the carburetor, and a valve interposed in the fuelpassage and directly operated by the throttle valve, said valvecomprising a valve seat, a valve head adapted to rest upon said seat atlow engine speeds, and a by-pass for passing a limited amount of fuelwhen the valve head rests upon the valve seat to closethe valve.

4'. A carburetor having a fuel chamber, an outlet and a throttle valvecontrolling said outlet, and comprising in combination a fuel passagecommunicating with said fuel chamber for delivering fuel drawn therefrominto said Venturi tubeby suction created by the passageof airtherethrough, and a valve in said passage having an aperturetherethrough restricting the fuel passage on closure'of said valve andoperable by said throttle valve to restrict said fuel passage atpredetermined positions of the said throttle valve. v

- 5. A carburetor having an induction chamber, a throttle valve disposedin said chamber, a means for maintaining a minimum depression in saidchamber and comprising in combination a primary air inlet having theform of a Venturitube, a fuel passage for conducting fuel to the throatof saidtube,

and a valve in said. fuel passage restricting the flow of fuel throughsaid passage when seated and operable by the throttle for permitting thefree flow of fuel therethrough when said valve is unseated atpredetermined positions of the throttle valve.

- 6. A fuel lift carburetor having a fuel chamber, an outlet and athrottle valve controlling said outlet, and comprising in com-v binationVenturi tube forming a primary air inlet, a fuel passage communicatingwith said fuel chamber for conducting fuel drawn therefrom into saidVenturi tube by suction created by the passage of air therethrough,

and a valve in-said passage restricting the fuel passage in the closedposition, and opened and closed by said throttle valve to restrict saidpassage and to permit the free flow tions of said throttle valve. 7 7. Afuel lift carburetor, comprising in combination an induction chamber, athrottle valve therein, a primary air inlet having the of fueltherethrough at predetermined posi- 1 form of a Venturi tube, a fuelpassage for conducting fuel to the throat of said tube, and means formaintaining a minimum'depression in said fuel passage including a valvein said fuel passage adapted when closed to supply fuel for normal andlow speed ranges, said valve being closed by said throttle valve atpredetermined positions thereof. a

8. A fuel lift carburetor having an induction chamber and a fuel nozzle,and compris-' ing the combination of a fuel chamber, a fuel passagecommunicating with said nozzle and an upper and lower connecting passagecom- 1 municating with said fuel passage and said fuel chamber, saidlower passage communi-- cat'ing with said fuel chamber below the fuellevel and said upper passage communicating "with theuppermost part ofsaid fliel chamber to conduct air bubbles in said fuel chamber to saidfuel passage and to co-minglethe .air'bUbbles with the fuel drawn fromsaid fuel chamber through the said-lower fuel passage. I 9. fuel lift"carburetor for drawing fuel o from a source of supply by suction,comprising avfuel chamber, a fuel nozzle for drawin'g fuel from saidfuel chamber and a fuel passageccommunicating at one end with saidnozzle and having a plurality of connecting passages at its opposite endcommunicating with said fuel chamber, a said connecting passage beingrestricted to provide a nozzle communicating with said chamber beneaththe level of fuel therein, and the other said connecting passagescomunicating with said chamber above the fuel level.

10. A fuel lift carburetor for drawing fuel from a source of supply bysuction, comprising in combination a fuel chamberfor receiving fuel fromthe fuel source, a valve controlling the supply of fuel received by saidchamber, a valve operating device in said fuel chamber, a fuel nozzle,and a fuel passage communicating at one end with said fuel nozzle andhaving a plurality of connecting passages at its opposite endcommunicating with said fuel chamber, said fuel nozzle providing suctionthrough said passages in said fuel chamber opposing the closing of saidvalve by said valve operating device.

In witness whereof, I hereunto subscribe my name this 26th day ofNovember, A. D.

ROBERT F. BRACKE.

